The broad long-term objective of this proposal is to improve vascular access longevity in chronic renal failure patients on hemodialysis using ultrasound evaluation. Synthetic graft failure after the first month is primarily due to clotting (thrombosis). After the graft thromboses, an underlying graft or draining vein stenosis is found in greater than 85 percent of patients, despite aggressive clinical monitoring for stenosis. Patent grafts with stenoses treated with percutaneous transluminal angioplasty (PTA) or surgical revision techniques have longer patency than thrombosed grafts after thrombectomy. Therefore, early stenosis detection with treatment of the hemodynamically significant stenoses found (in patent grafts) should increase graft longevity, thereby decreasing the substantial costs associated with graft failure. We propose to actively test two graft surveillance strategies. This study will test the hypothesis that triannual ultrasound monitoring and percutaneous treatment of detected stenoses will improve hemodialysis graft longevity compared to aggressive clinical monitoring. Specific Aims: To test the hypothesis that: 1). Triannual color flow ultrasound (US) surveillance of hemodialysis grafts can diagnose stenoses that are not detected during aggressive clinical monitoring. 2). PTA of hemodynamically significant stenoses detected by ultrasound surveillance will approximately double graft longevity, from the current 16 months. 3). To determine the ultrasound and angiographic measurement parameters that most accurately predict the longevity of the PTA result. 4). To assess the cost-effectiveness of early color flow US graft stenoses detection and intervention versus aggressive clinical monitoring. Health Relatedness: If color flow US monitoring in addition to aggressive clinical monitoring increases graft longevity and is cost effective as compared to aggressive clinical monitoring alone, this would have important implications for patient management. Increased graft longevity should lead to improved patient quality of life, secondary to a decreased need for thrombectomies, temporary access catheters and surgical placement of new grafts. Research Design and Methods: A randomized, prospective clinical trial will compare triannual color flow US graft monitoring in addition to aggressive clinical monitoring, to aggressive clinical monitoring alone. PTA or surgical revision of hemodynamically significant stenoses detected will be performed. Access patency will be followed for at least 2 years, or until placement of a new access. All other aspects of the patients' medical and dialysis care will follow usual medical standards.